The present invention relates to apparatus for displaying sign posters, and particularly outdoor advertising posters wherein the display is of relatively large area. Outdoor advertising billboards typically range in size from about eight feet by ten feet to sizes in excess of twenty feet by eighty feet. According to the state of the art relating to advertising billboards in the size range of up to twelve feet by twenty-four feet, the material which is displayed thereon is typically printed in advance in sections, and the sections are pasted to the board and pieced together by a skilled craftsman, who is trained in handling fairly large sections of an outdoor advertising poster and in properly registering the sections together. Billboards larger than about twelve feet by twenty-four feet are typically hand painted by skilled painters.
The lighting of large outdoor advertising billboards for nighttime display is accomplished by lighting fixtures which project forwardly from the poster, either from a top or bottom edge, so that the light fixture is directed toward the poster for front lighting illumination. The state of the art in outdoor advertising has not yet permitted a satisfactory billboard with rear illumination. Of course, small size advertising posters, of up to several feet on a side, have been developed using photographic enlarging techniques wherein an enlargement is photographically placed on a film surface and the film surface is mounted on a transparent surface and is illuminated by means of light from the rear. While these small, photographically enlarged posters create a striking and dramatic effect, it has not yet been possible to extend the technology to commercial billboard sizes such as are typically found along highways and streets.
If ordinary billboard techniques are utilized in attempting to create a back-lighted, large billboard, the imperfect alignment of adjacent sections of the large poster create light cracks or opaque strips which detract from the quality of the piece. There has heretofore been no known effective way to solve the problem of registering sectional pieces of a larger billboard poster in a manner which permits backlighting and avoids the adverse effects of poor registration over mating sections of the poster.